he could hire help if he wanted to
Or not to. Again, hiring people turning a person from artist to management worker, at the same time shifting game from piece of guilty pleasure to entertainment product/service. Oni does not receive money on basis of empty promises to make A TONS OF NEW CONTENT JUST GIVE ME MONEY. He provides content of the same quality on stable basis, offering exactly that. People are ready and willing to pay for it.
Amount of money he makes does not have anything to do with it. It can be 100$ or 10,000,000$, people are paying for what they are stably getting, not for empty promises. That is a fair market price.